Rev. Dr. Irving — An Ancient Esfuary. 357 



a specimen of the latter in the British Museum with the Endoceras 

 zaddachi of Schroder,^ I can see no reason for changing the opinion 

 I formed about it when writing part i. of the Catalogue of Fossil 

 Cephalopoda, viz. that the two species are identical. The vaginattts 

 of Eichwald (non Schlotheim) becomes therefore a synonym of 

 zaddachi, Schroder, and not vice versa, as in my Catalogue. 



JV. — Physical Studies of an Ancient Estuary.^ 

 Ey the Eev. A. Irving, D.Sc, F.G.S. 



IT is needless to recapitulate, for the information of the readers 

 of the Geological Magazine, all the incidents which are 

 known to accompany the formation of new land by rivers, or to 

 repeat the descriptions which have been given of the more remark- 

 able instances of them, such as those of the Nile, the Mississippi, 

 the Ganges, the Rhone, the Po, and the Danube. These have been 

 scientifically discussed long ago, bj' Lyell in his Principles. The 

 object of this paper is rather to suggest how a careful collation 

 of such facts as may be learned in connexion with the formatioa 

 of modern deposits at the mouths of great rivers, or in great 

 estuarine areas (such as the Wash), which receive a number of 

 streams from widely-extended inland catchment-basins, may throw 

 light upon the history of older formations of the same kind, and 

 more especially of those of Tertiary times, during which many 

 important changes were wrought in the physiography of the 

 continent of Europe. 



As instances of the work done by rivers in making new land, 

 especially when aided by tidal action, within historic times, one 

 might cite the case of the Po, co-operating with the Alpine rivers 

 which come down from the Venetian Alps, forming a great 

 series of lagoons around the head of the Adriatic Sea, or the 

 advance of the land upon the sea, which has placed the town of 

 Eavenna (a sea-port under Augustus) several miles from the shore ; 

 or again, the proved advance of the delta of the Ehone upon the 

 Mediterranean, which has been found to place the Tower of St. 

 Louis a league or so further from the shore in the short space of 

 a single century. But these, and such cases as these, are hardly 

 necessary, when we have here in our own Humber the formation 

 of Sunk Island within the course of a few centuries. This island 

 (so-called) is probably well known to Yorkshiremen, but perhaps 

 a comparatively small number of them are aware of its importance, 

 from a geological point of view, as a testimony to the work done by 

 rivers in compensating to some extent the work of degradation and 

 denudation of the higher parts of the country, which is ever in 

 progress, year in year out. This island has been formed by the 

 deposition of sedimentary materials by the rivers Ouse, Trent, and 

 Hull, as their onward flow has been checked, and their transporting 



^ Schrift. der pbysikal-bkonom. GeseU. zu Konigsberg, Jahrg. sxii. Abth. i. p. 93, 

 Taf. iv. S. 5, a-d. 

 2 Paper read before the British Association, Section C, at the Leeds Meeting, 1890. 



